For those of a certain age, the violence and rising tensions we are witnessing in the United States have stirred feelings of anxiousness that are familiar. We have seen this movie before.
My family was glued to our television set in the summer of 1967, watching news coverage of a five-day riot in Detroit, which was less than an hour's drive from our home. It began when police raided an unlicensed drinking club in the early-morning hours of July 23. The arrests of more than 80 black people found in the after-hours joint incited a mob outside.
Pretty soon it was on, the protest becoming an outlet for broader black anger associated with an array of issues, including police brutality and economic deprivation.
Rioters set entire city blocks on fire. When the smoke finally cleared, after nearly a week, 43 people were dead, nearly 2,000 were injured and 7,000 arrested; an estimated 1,000 buildings were damaged or destroyed.
The following year, protests spread across the United States, sparked by a poor economy, social and racial injustice, and the Vietnam War. The political assassinations of Martin Luther King Jr. and Bobby Kennedy created a level of angst and uncertainty that was palpable.
Related: Munich, Nice, Turkey, Brexit, Trump: It's all connected
Across the border in Canada we asked: What is going on with our neighbours? We are asking the same question today.
Not everyone, however, is surprised by the police slayings, mass shootings and racial conflict, including Peter Turchin, an evolutionary biologist and mathematician at the University of Connecticut. He is a big name in the field of study known as cliodynamics, in which scientists attempt to discern consequential archetypes in history. Dr. Turchin's research has tracked upsurges in violence in the United States since the late 1870s and found that every 50 years or so there is a peak in the level of bloodshed.
The last such period was the late 1960s and early 1970s. His modelling suggests we are due for another right about now.
It is his contention that these swells of hostility act much like a forest fire – there is an explosion of violence at the outset that is sustained over a certain period of time. Inevitability, the public yearns for the return of relative peace and stability.
Eventually, Dr. Turchin argues, the generation scarred by the civil violence and the resulting deep feelings of fear and unease dies off. A new generation not damaged emotionally by the earlier epoch of carnage takes over.
"If the long-term forces that brought about the first outbreak of internal hostilities are still operating, then the society will slide into the second civil war," Dr. Turchin wrote in a 2012 article in the Journal of Peace Research. "As a result, periods of intense conflict tend to recur with a period of roughly two generations (40 to 60 years)."
It would seem the United States has been building toward this moment. The number of shooting rampages and massacres has increased tenfold between 1960 and 2010, Dr. Turchin notes. Meanwhile, the political discourse has become increasingly frayed and divisive, more so then at any time in recent history. It is a reflection of the general mood in the country. Donald Trump is a product of the anger and frustration that is out there, certainly among white people who feel they are losing the country they love.
Dr. Turchin thinks it is all a harbinger of greater danger on the way; the proverbial canary in the coal mine, an early-warning indicator that something is changing for the worse. The research and patterning he has done suggests this next age of violence and aggression will be far worse than the last one because wages, standards of living and a number of other measures generally associated with social stability are much worse this time around.
Whether he turns out to be right remains to be seen. But from our safe perch here in Canada, something certainly seems different about what is taking place in the United States, something we have not seen or felt for some time.
It is a feeling that takes me back to a living room nearly 50 years ago, watching a television and wondering how people could ever get so angry.
Gary Mason